Blood samples are commonly obtained from a patient using either an arterial blood gas syringe for obtaining arterial blood samples from a patient or by using a vacuum blood collection tube and blood collection tube holder for obtaining venous blood samples from a patient.
In the field of arterial blood gas syringes, numerous designs have been developed in an effort to prevent exposure of a collected blood sample to the atmosphere or to allow for the removal of contaminant gases from the syringe as the blood sample is being drawn. Arterial blood gas syringes typically include a syringe barrel, a standard needle and a plunger rod with a piston member on the distal end thereof. In many of these syringes, the piston member and/or the plunger rod include a venting structure to prevent oxygen or carbon dioxide from reacting with the arterial blood sample so that an accurate measurement of the components of the blood sample may be performed. U.S. Pat. No. 4,615,341 granted to Marzolf et al; U.S. Pat. Nos. 4,373,535 and 4,448,206 granted to Martell and U.S. Pat. No. 4,572,210 granted to McKinnon are illustrative of some of the arterial blood gas syringe designs which include a venting structure associated with the syringe. These devices are designed to allow the physician or nurse to obtain the desired blood sample directly from an artery of the patient by piercing the skin of the patient with the preattached needle.
Another approach to obtaining a blood sample from a patient is illustrated in U.S. Pat. No. 4,192,320 granted to Megahed. The Megahed patent discloses the use of an adaptor for use with a conventional syringe assembly and a conventional blood collection tube holder to obtain a blood sample from the vein of the patient. The adaptor is described as being of a conventional elastomeric, self-sealing material which is frictionally retained on the distal end of the conventional syringe assembly. Once the adaptor has been placed on the distal end of the conventional syringe assembly, this combination is inserted into a blood collection tube holder which has previously been inserted into the vein of the patient. The adaptor and syringe assembly are then inserted into the blood collection tube holder until the proximal end of the double ended needle on the blood collection tube holder pierces the adaptor. The blood sample is then obtained from the vein of the patient by a combination of the patient's venous pressure plus the retraction of the plunger of the syringe assembly to aspirate the blood into the syringe chamber. Once a sufficient venous blood sample has been obtained, the adaptor and syringe assembly are removed from the blood collection tube holder and the collected venous blood sample is then analyzed.